The present invention pertains to a method for adjusting or altering the play between brake linings and friction surfaces of motor vehicle brakes by means of controllable and adjustable lifting and return movements of the brake linings.
The present invention also pertains to a device for adjusting or altering the play between brake linings and friction surfaces of motor vehicle brakes, wherein said device contains a brake control/brake regulator for acquiring and processing electronic signals delivered by a brake pedal sensor and, optionally, additional sensors, and for actuating electromechanical brake actuators.
In recent years, electromechanical brake systems, namely so-called brake systems of the brake-by-wire type, have been introduced on the market and developed for motor vehicles, in particular, passenger cars. In brake systems of this type, the influence of the force applied to the brake pedal by the driver is measured by a sensor, converted into an electronic signal and forwarded to brake actuators. Such a brake actuator is assigned to each wheel of the motor vehicle. These brake actuators usually exert a tension force on the brake linings by means of a device that is driven by an electric motor, i.e., the brake linings are pressed against the disk of the wheel brake. One embodiment of such an electromechanical disk brake system for motor vehicles is, for example, known from DE 40 21 572 A1.
A method and the device of the type discussed above which allow an electronically controlled adjustment of the play between the brake linings and the friction surfaces of motor vehicle brakes is known from DE 44 33 377 A1. This method and the corresponding device utilize a brake control/brake regulator which, except during the brake actuating phases, make it possible to adjust a defined play between the brake linings and the respective friction surfaces. In that case, it is particularly important to optimize the lifting and return movements in such a way that the lifting movement ceases once a complete release of the brakes and consequently an unobstructed turning of the wheels is realized, and that a fast engagement between the brake linings and the friction surfaces is achieved. The active lifting of the brake linings off of the respective friction surfaces reduces the residual moment of friction, and consequently the wear of the brake linings. In addition, the fuel consumption of the motor vehicle is correspondingly reduced. The process of lifting the brake linings off of the respective friction surfaces is realized with the aid of an electric actuator that operates in the reverse direction and may also serve for actuating the brake during normal braking mode. In this case, the brake control/brake regulator may also serve for regularly increasing and decreasing the play by a small amount, e.g., after each time the engine is started, in order to ensure the unobstructed movement of brake components to be moved in mechanical fashion. In addition, it is possible to actuate the brakes briefly and regularly during wet weather in order to remove the film of liquid, such that the brake actuation cannot be noticed by the driver.
According to this known method and the respectively known device, it is of primary importance to ensure the basic function of an active, complete release of the brake. This means that a play of such a size is adjusted that, once the brake is actuated, the play initially must be overcome before a braking force is generated. However, the process of overcoming this play requires time and increases the braking time as well as the stopping distance.
Consequently, it is an object of the present invention to avoid the disadvantages of known systems.